Waste incineration disposal method

ABSTRACT

A waste is dry-distilled in a gasification furnace and generated combustible gas is combusted in a combustion furnace. A temperature in the combustion furnace is set to be substantially constant at a first preset temperature or more. When the temperature in the combustion furnace is greater than the first preset temperature by combustion of other fuels, the combustible gas is introduced. When the temperature in the combustion furnace reaches a second preset temperature or more by the combustion of only the combustible gas, the combustion of the other fuels is finished. When the temperature in the combustion furnace falls below a third preset temperature the combustion of the other fuels is resumed. When the temperature in the gasification furnace falls below a fourth preset temperature, the combustion of the other fuels is finished.

TECHNICAL FIELD

The present invention relates to a waste incineration disposal method.

BACKGROUND ART

In recent years, it has been pointed out that dioxins are generatedduring incineration disposal of a waste. In many cases, the wastecontains chlorine. Therefore, when the waste is combusted at atemperature of 250 to 350° C., chlorine liberated from the waste, andhydrocarbon generated by incomplete combustion of resins react with eachother using a catalyst of a heavy metal contained in the waste, anddioxins are generated.

In order to prevent dioxins emission by the incineration disposal of thewaste, it is said to be effective to retain the waste at 800° C. or morefor two seconds or more, and completely thermally decompose thegenerated dioxins. However, even when the wastes such as miscellaneousliving wastes, paper, and soft vinyl chloride are incinerated, it isdifficult to stably keep the wastes at 800° C. or a higher temperature.Therefore, in order to prevent the dioxins emission, in general, thewastes are combusted together with other fuels such as a heavy oil, andthereby stably incinerated at 800° C. or more. In this case, since theother fuels have to be combusted together with the wastes through theentire incineration disposal process, a large amount of other fuels arerequired, and a running cost increase cannot be avoided.

Additionally, the present applicant has proposed an apparatus disclosedin Japanese Patent Application Laid-Open No. 135280/1990 as anincineration disposal apparatus of wastes such as a waste tire.

The apparatus disclosed in the above publication is constituted of afully closed gasification furnace, and a combustion furnace connected tothe gasification furnace via a gas passage a part of the waste iscombusted in the gasification furnace, and a combustible gas generatedby dry distillation of the other part of the waste with the combustionheat is introduced into the combustion furnace to completely combustedthe waste. Details of incineration disposal of the waste by theapparatus will next be described.

During the incineration disposal of the waste by the apparatus, firstthe waste contained beforehand in the fully closed gasification furnaceis ignited, a part of the waste is combusted, and the other part thereofis dry-distilled by the combustion heat. Moreover, the combustible gasgenerated by the dry distillation is introduced into the combustionfurnace disposed outside the gasification furnace via the gas passage.

Subsequently, a combustion flame is supplied to the introducedcombustible gas to ignite the gas, thereby starting combustion of thecombustible gas.

Next, when the dry distillation progresses and the combustible gas isstably generated, an amount of generated combustible gas graduallyincreases, and a combustion temperature of the combustible gas detectedas a temperature T₂ in the combustion furnace gradually rises as shownin FIG. 3. In this case, the temperature T₂ in the combustion furnacereaches a temperature T_(2a) at which the combustible gas canspontaneously and stably continue the combustion by its own combustionheat, and the supply of the combustion flame is then stopped.

Subsequently, oxygen necessary for complete combustion of thecombustible gas is supplied to the combustion furnace in accordance withthe amount of the combustible gas introduced into the combustionfurnace. Additionally, while the combustible gas is completelycombusted, the temperature T₂ in the combustion furnace is detected asthe combustion temperature of the combustible gas, an amount of oxygensupplied to the gasification furnace is controlled in accordance with achange of temperature T₂, and the amount of the combustible gasgenerated by the dry distillation is adjusted. In the apparatus, thetemperature T₂ in the combustion furnace can be maintained in thismanner to be substantially constant at a temperature T_(2b) higher thana temperature T_(2a) at which the combustible gas spontaneously andstably continues the combustion.

In the apparatus, when the dry distillation further progresses, aportion of the waste able to be dry-distilled in the gasificationfurnace is reduced. Even when the amount of oxygen supplied to thegasification furnace is increased, a sufficient amount of combustiblegas for maintaining the temperature T₂ in the combustion furnace to besubstantially constant at the temperature T_(2b) cannot be generatedThen, the temperature T₂ in the combustion furnace gradually drops, thedry distillation and combustion of the waste in the gasification furnaceare finished and the waste is ashed. Additionally, a temperature in thegasification furnace is shown as T₁ in FIG. 3.

As a result, according to the apparatus, the dry distillation of thewaste and the complete combustion of the combustible gas can stably beperformed, and in a stage in which the combustible gas spontaneously andstably, continues the combustion, the temperature in the combustionfurnace can be maintained to be substantially constant at a preset orhigher temperature.

Here, when the apparatus disclosed in the above publication is used inthe incineration disposal of the waste, the waste is regulated so as togenerate the combustible gas having heat amount for setting a combustiontemperature at which dioxins can thermally be decomposed, for example,at 800° C. or more. Then, in the stage in which the combustible gasspontaneously and stably continues the combustion, the temperature inthe combustion furnace can be maintained to be substantially constant at800° C. or more. Therefore, to keep the temperature in the combustionfurnace at 800° C. or more, it is unnecessary to combusted other fuelssuch as a heavy oil, and the dioxins emission can be prevented at a lowcost.

However, during the aforementioned waste incineration disposal, in thestage in which the combustible gas spontaneously and stably continuesthe combustion after the start of the waste dry distillation, and in thestage in which the portion of the waste able to be dry-distilled in thegasification furnace is reduced and the waste is ashed after the stageof the spontaneous and stable continuation of the combustion of thecombustible gas, the temperature in the combustion furnace does notreach 800° C. and there is a disadvantage that dioxins are emitted.

DISCLOSURE OF THE INVENTION

To solve the aforementioned disadvantage, an object of the presentinvention is to provide a waste incineration disposal method which canprevent dioxins emission and reduce running costs.

To achieve the aforementioned object, the waste incineration disposalmethod of the present invention comprises steps of: combusting a part ofa waste contained in a gasification furnace, and dry-distilling theother part of the waste by a combustion heat; and introducing acombustible gas generated by the dry distillation into a combustionfurnace to combusted the combustible gas. When the combustible gas iscombusted in the combustion furnace, oxygen required for the combustionis supplied to the combustion furnace in accordance with an amount ofthe combustible gas introduced into the combustion furnace to combustedthe combustible gas, an amount of oxygen supplied to the gasificationfurnace is controlled in accordance with a temperature change in thecombustion furnace by the combustion of the combustible gas in thecombustion furnace, the amount of the combustible gas generated by thedry distillation is adjusted, and the temperature in the combustionfurnace is maintained to be substantially constant at a first presettemperature or more. In the waste incineration method, the wasteregulated to generate the combustible gas having a heat amount forsetting the temperature in the combustion furnace at the first presettemperature or more during the combustion is contained in thegasification furnace. Fuels other than the combustible gas are combustedin the combustion furnace prior to ignition of the waste. When thetemperature in the combustion furnace reaches the first presettemperature or more, the waste is ignited to start dry distillation, andthe generated combustible gas is combusted with the other fuels. Whenthe temperature in the combustion furnace reaches a second presettemperature higher than the first preset temperature or more by thecombustion of only the combustible gas, the combustion of the otherfuels is finished, the temperature in the combustion furnace ismaintained to be substantially constant at the second preset temperatureor more, and only the combustible gas is combusted. When the temperaturein the combustion furnace falls below a third preset temperature lowerthan the substantially constant temperature and higher than the firstpreset temperature, the combustion of the other fuels is resumed, thecombustible gas is combusted with the other fuels, and the temperaturein the combustion furnace is maintained at the first preset temperatureor more. When the temperature in the gasification furnace falls below afourth preset temperature lower than a maximum temperature in thegasification furnace, the combustion of the other fuels is finished.

In the method of the present invention, the apparatus disclosed in theaforementioned publication is used, the waste regulated to generate thecombustible gas having the heat amount for setting the temperature inthe combustion furnace at the first preset temperature or more duringcombustion is contained in the gasification furnace, and the wasteincineration disposal is performed. Here, the first preset temperatureis a temperature at which dioxins can thermally be decomposed, and isconcretely set at 800° C. or more.

In this constitution, when the combustible gas generated by the drydistillation of the waste in the gasification furnace is combusted inthe combustion furnace, in the stage in which the combustible gasspontaneously and stably continues the combustion, the other fuels suchas a heavy oil are not combusted, the temperature in the combustionfurnace is maintained to be substantially constant at 800° C. or more bythe heat amount of the combustible gas itself and the dioxins emissioncan be prevented.

Moreover, in the method of the present invention, prior to ignition ofthe waste, the fuels other than the combustible gas are combusted in thecombustion furnace, and the combustion furnace interior is heated at thefirst preset temperature or more before the combustible gas isintroduced into the combustion furnace. Furthermore, when thetemperature in the combustion furnace reaches the first presettemperature or more, the waste in the gasification furnace is ignitedthereby starting the dry distillation of the waste. As a result, whilethe temperature in the combustion furnace is not less than the firstpreset temperature, the combustible gas generated by the drydistillation is introduced into the combustion furnace, and the dioxinsemission in the initial stage of dry distillation can be prevented.

In the initial stage of the dry distillation, since the dry distillationis not sufficiently stabilized, the amount of the generated combustiblegas is not stable, and it is difficult to maintain the first preset orhigher temperature in the combustion furnace by the combustion of onlythe combustible gas. To solve this problem, in the method of the presentinvention, the combustible gas is combusted with the other fuels in theinitial stage of the dry distillation, and the first preset or highertemperature is thereby maintained in the combustion furnace. Moreover,when the temperature in the combustion furnace reaches the second presettemperature higher than the first preset temperature, or more by thecombustion of only the combustible gas, it is judged that thecombustible gas can spontaneously and stably continue the combustion,and the combustion of the other fuels is finished. As a result, from thestart of the dry distillation until the combustible gas canspontaneously and stably continue the combustion, the dioxins emissioncan be prevented.

After the combustion of the other fuels is finished, the temperature inthe combustion furnace is maintained to be not less than the secondpreset temperature, that is, to be substantially constant at the firstpreset temperature or more, and only the combustible gas is combusted.Therefore, as described above, the dioxins emission can be prevented inthis stage.

When the waste dry distillation progresses in the gasification furnaceand the portion able to be dry-distilled is reduced, the amount ofgenerated combustible gas decreases, and the temperature in thecombustion furnace starts dropping from the temperature which issubstantially constant at the second preset temperature or more.However, in this stage, the temperature in the gasification furnace ishigh, and there is still a possibility that dioxins are generated.

To solve the problem, in the method of the present invention, next, whenthe temperature in the combustion furnace starts dropping from thesubstantially constant temperature being not less than the second presettemperature, the combustion of the other fuels is resumed at a point atwhich the temperature falls below the third preset temperature higherthan the first preset temperature, so that the temperature in thecombustion furnace is not lower than the first preset temperature. Whenthe combustible gas is combusted with the other fuels, the portion ofthe waste able to be dry-distilled in the gasification furnace isreduced. Even when the amount of the generated combustible gas isreduced, the temperature in the combustion furnace is maintained at orabove the first preset temperature.

Moreover, when the temperature in the gasification furnace falls belowthe fourth preset temperature lower than the maximum temperature in thegasification furnace, it is Judged that the dioxins are not contained inthe combustible gas, and the combustion of the other fuels is finished.Here, the fourth preset temperature is concretely set to be less than adioxins generation temperature. As a result, the dioxins emission can beprevented in the stage in which the portion of the waste able to bedry-distilled in the gasification furnace is reduced and the waste isashed.

When the combustion of the other fuels is finished, the portion of thewaste able to be dry-distilled in the gasification furnace is finallyeliminated, the waste is ashed, and extinction naturally occurs.Moreover, even in the combustion furnace, with the decrease of theportion of the waste able to be dry-distilled in the gasificationfurnace, the amount of the combustible gas is reduced, the spontaneouscombustion cannot be maintained, and extinction naturally occurs. As aresult, the incineration disposal according to the method of the presentinvention is naturally finished.

As described above, according to the method of the present invention,from the start of the waste dry distillation until the temperature inthe gasification furnace falls below the dioxins generation temperature,the temperature in the combustion furnace is maintained at the firstpreset temperature or more. Therefore, the dioxins emission can securelybe prevented over the entire waste incineration process.

Moreover, in the method of the present invention, in the stage after thewaste dry distillation is started and before the combustible gasspontaneously and stably continues the combustion, and in the stage inwhich the portion of the waste able to be dry-distilled in thegasification furnace is reduced and the waste is ashed after the stageof the spontaneous and stable continuation of the combustion of thecombustible gas, the other fuels are combusted. While the combustiblegas spontaneously and stably continues the combustion, the other fuelsare not combusted. Therefore, the use amount of the other fuels issaved, and the running costs can be reduced.

Moreover, in the method of the present invention, in a period from thewaste ignition until the temperature in the combustion furnace reachesthe second preset temperature or more by the combustion of only thecombustible gas, the combustion of the other fuels is intermittentlyperformed by stopping the combustion of the other fuels when thetemperature in the combustion furnace reaches the second presettemperature or more, and again igniting the waste when the temperaturein the combustion furnace falls below the second preset temperatureafter the stop. When the temperature in the combustion furnace is notless than the second preset temperature even after the combustion of theother fuels, the intermittent combustion of the other fuels is finished.

In the method of the present invention, when the combustion of the otherfuels is stopped, the temperature in the combustion furnace depends onthe combustion of only the combustible gas. Therefore, a combustionstate of the combustible gas can be detected by checking the temperaturein the combustion furnace after stopping the combustion of the otherfuels. Moreover, in the period, when the temperature in the combustionfurnace reaches the second preset temperature or more, the combustion ofthe other fuels is stopped, and the temperature in the combustionfurnace then falls below the second preset temperature, it is judgedthat the temperature in the combustion furnace does not possibly reachthe first preset temperature or more by the combustion of only thecombustible gas, and the other fuels are ignited again. Furthermore,when the temperature in the combustion furnace reaches the second presettemperature or more after the re-ignition, the combustion of the otherfuels is stopped again, and the aforementioned operation is repeated.

Moreover, when the temperature in the combustion furnace is maintainedat the second preset temperature or more even after the stop of thecombustion of the other fuels, the temperature in the combustion furnacesecurely reaches the first preset temperature or more by the combustionof only the combustible gas, it is judged that the combustible gas canspontaneously and stably continue the combustion, and the combustion ofthe other fuels is finished.

Furthermore, in the method of the present invention, in a period fromwhen the temperature in the combustion furnace falls below the thirdpreset temperature until the temperature in the combustion furnace fallsbelow the fourth preset temperature, the combustion of the other fuelsis intermittently performed by stopping the combustion of the otherfuels when the temperature in the combustion furnace reaches the thirdpreset temperature or more, and again igniting the waste when thetemperature in the combustion furnace falls below the third presettemperature after the stop. When the temperature in the combustionfurnace falls below the third preset temperature even after there-ignition, the combustion of the other fuels is continuouslyperformed, and the temperature in the combustion furnace is maintainedat the first preset temperature or more. Thereafter, when thetemperature in the gasification furnace falls below the fourth presettemperature, the combustion of the other fuels is finished.

In the method of the present invention, when the temperature in thecombustion furnace falls below the third preset temperature, thecombustion of the other fuels is resumed. Moreover, when the temperaturein the combustion furnace reaches the third preset temperature or moreby the combustion of the other fuels, the combustion state of thecombustible gas can be detected as described above by stopping thecombustion of the other fuels and checking the temperature in thecombustion furnace after the stop.

Therefore, in the period, when the temperature in the combustion furnacereaches the third preset temperature or more, the combustion of theother fuels is stopped, and the temperature in the combustion furnacefalls below the third preset temperature, it is then judged that thetemperature in the combustion furnace does not possibly reach the firstpreset temperature or more by the combustion of only the combustiblegas, and the other fuels are ignited again. Moreover, when thetemperature in the combustion furnace reaches the third presettemperature or more after the re-ignition, the combustion of the otherfuels is stopped again, and the aforementioned operation is repeated.

Furthermore, when the temperature in the combustion furnace falls belowthe third preset temperature even after the re-ignition of the otherfuels, it is judged that the temperature in the combustion furnacecannot be maintained at the first preset temperature or more by thecombustion of only the combustible gas, the combustion of the otherfuels is continuously performed, and the temperature in the combustionfurnace is maintained at the first preset temperature or more.Thereafter, when the temperature in the gasification furnace falls belowthe fourth preset temperature, as described above, it is judged that thegas introduced into the combustion furnace from the gasification furnacecontains no dioxins, and the combustion of the other fuels is finished.

In the method of the present invention, as described above, in theperiod from the waste ignition until the temperature in the combustionfurnace reaches the second preset temperature or more by the combustionof only the combustible gas, or in the period from when the temperaturein the combustion furnace falls below the third preset temperature untilthe temperature in the gasification furnace falls below the fourthpreset temperature, the combustion of the other fuels is intermittentlyperformed, so that amount of the other fuels can be saved, and therunning costs can be reduced.

Moreover, in the method of the present invention, in a period from whenthe temperature in the combustion furnace falls below the third presettemperature until the temperature in the gasification furnace fallsbelow the fourth preset temperature, the temperature in the gasificationfurnace is detected every predetermined time. After it is consecutivelydetected predetermined times that the temperature in the gasificationfurnace is less than the maximum temperature in the gasificationfurnace, and the temperature in the gasification furnace falls below thefourth preset temperature, the combustion of the other fuels isfinished.

When the part of the waste able to be dry-distilled is reduced in thegasification furnace, the heat amount consumed in the dry distillationis not consumed, and the temperature in the gasification furnace rapidlystarts rising by red heat of the waste. Moreover, when the red heatingof the waste is finished and ashing starts, the temperature in thegasification furnace in turn drops from the maximum temperature at whichthe waste is red-heated.

However, since a material, capacity, and the like of the waste subjectedto the incineration disposal by the method of the present invention arevarious, the red heating does not uniformly shift to the ashing. Evenwhen the surface of the waste is ashed, a lower layer part is stillred-heated, and the waste whose red heating is retarded sometimesremains. In this case, the temperature rises again by the red heating ofthe waste. This tendency becomes more remarkable when the gasificationfurnace has a large capacity.

Moreover, in the method of the present invention, as described above,the temperature in the gasification furnace is detected everypredetermined time, it is consecutively detected predetermined timesthat the temperature in the gasification furnace is less than themaximum temperature in the gasification furnace, and it is then judgedthat the waste in the gasification furnace entirely shifts to an ashingstage. Thereafter, when the temperature in the gasification furnacefalls below the fourth preset temperature, the combustion of the otherfuels is finished. The dioxins emission caused by re-rising of thetemperature in the gasification furnace can securely be prevented.

Furthermore, according to the method of the present invention, when thecombustible gas generated by the dry distillation of the waste in thegasification furnace is introduced into the combustion furnace andcombusted, a part of the combustible gas is dispensed and condensed, andoil content is collected and used as the other fuels.

In the method of the present invention, combustion assistant oils suchas a heavy oil can be used as the other fuels. When only the combustionassistant oil is used, however, a burden added by a fuel becomes heavy.Then, the burden can be alleviated by dispensing a part of thecombustible gas, and adding the condensed and collected oil content tothe other fuels.

In a stage in which the dry distillation progresses well, a sufficientamount of combustible gas is generated to maintain the temperature inthe combustion furnace to be substantially constant at the first presettemperature or more. Therefore, even when a part of the combustible gasis dispensed, the temperature in the combustion furnace is notinfluenced, and the substantially constant temperature is maintained.Moreover, when a combustible component contained in the combustible gasis condensed and liquefied, the component can easily be collected as theoil content.

Moreover, in the method of the present invention, when the other fuelsare combusted, oxygen heated by the heat of the combustion furnace issupplied to the combustion furnace.

When heated oxygen is supplied to the combustion furnace, the heatamount consumed by heating oxygen in the combustion furnace is saved,and the combustion temperature of the combustible gas rises. Therefore,when the other fuels are combusted, the fuel can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system constitution diagram showing one embodiment of anapparatus for dry distillation, gasification and incineration disposalof a waste for use in an incineration disposal method of the presentinvention, and

FIG. 2 is a graph showing changes of a temperature in a gasificationfurnace and a combustion temperature in a combustion furnace with elapseof time in the incineration disposal method of the present invention.Moreover,

FIG. 3 is a graph showing the changes of the temperature in thegasification furnace and the combustion temperature in the combustionfurnace with elapse of time in a conventional incineration disposalmethod.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described in more detailwith reference to the accompanying drawings.

As shown in FIG. 1, an apparatus for dry distillation, gasification andincineration disposal of a waste according to the present embodiment isprovided with a gasification furnace 1 for containing a waste A which isa mixture of various wastes mainly of waste tires; and a combustionfurnace 3 connected to the gasification furnace 1 via a gas passage 2.An introduction port 5 provided with an openable/closable introductiondoor 4 is formed in an upper surface of the gasification furnace 1, anda waste A such as a waste tire can be introduced into the gasificationfurnace 1 via the introduction port 5. Moreover, while the introductiondoor 4 is closed, the gasification furnace 1 is substantially shut offfrom the outside.

A water jacket 6 isolated from the interior of the gasification furnace1 is formed as a cooling structure on an outer periphery of thegasification furnace 1. Water is supplied to the water jacket 6 from awater supply device (not shown), and an interior water amount ismaintained at a predetermined water level.

A lower part of the gasification furnace 1 is formed in a frustoconicalshape which projects downward. An empty chamber 7 isolated from theinterior of the gasification furnace 1 is formed in the outer peripheryof the lower part of the frustoconical shape. The empty chamber 7 isconnected to the interior of the gasification furnace 1 via a pluralityof air supply nozzles 8 disposed in an inner wall of the gasificationfurnace 1.

The empty chamber 7 of the lower part of the gasification furnace 1 isconnected to a dry distillation oxygen supply path 9. The drydistillation oxygen supply path 9 is connected to an oxygen (air) supplysource 11 constituted of a blower fan via a main oxygen supply path 10.The dry distillation oxygen supply path 9 is provided with a controlvalve 12, and an open degree of the control valve 12 is controlled by avalve drive unit 13. In this case, the valve drive unit 13 is controlledby a control device 14 constituted of an electronic circuit includingCPU, and the like.

Furthermore, an igniter 15, controlled by the control device 14, forigniting the waste A contained in the gasification furnace 1 is attachedto the lower part of the gasification furnace 1. The igniter 15 isconstituted of an ignition burner or the like, and supplies combustionflame to the waste A by combusting a fuel supplied from a fuel supplydevice 16 in which combustion assistant oils such as a heavy oil arestored via a fuel supply path 17.

The combustion furnace 3 is constituted of a burner section 18 formixing a combustible gas generated by dry distillation of the waste Awith oxygen (air) necessary for complete combustion of the gas, and acombustion section 19 for combusting the combustible gas mixed withoxygen. The combustion section 19 is connected to the burner section 18on the tip end side of the burner section 18. The gas passage 2 isconnected to the rear end of the burner section 18, and the combustiblegas generated by the dry distillation of the waste A in the gasificationfurnace 1 is introduced into the burner section 18 via the gas passage2.

An empty chamber 20 isolated from the interior of the burner section isformed in the outer periphery of the burner section 18, and the emptychamber 20 is connected to the interior of the burner section 18 via aplurality of nozzle holes 21 formed in the inner periphery of the burnersection 18. The empty chamber 20 is connected to a combustion oxygensupply path 22 branched from the main oxygen supply path 10. Thecombustion oxygen supply path 22 is provided with a control valve 23,and the open degree of the control valve 23 is controlled by a valvedrive unit 24. In this case, the valve drive unit 24 is controlled bythe control device 14.

A combustion device 25, controlled by the control device 14, forcombusting the combustion assistant oils such as the heavy oil suppliedfrom the fuel supply device 16 via the fuel supply path 17 is attachedto the rear end of the burner section 18. The combustion device 25 isconstituted of an ignition burner or the like, and combusts thecombustion assistant oil. Additionally, the combustion device 25 is alsoused in igniting the combustible gas introduced into the burner section18.

A duct 26 a for discharging waste gas after complete combustion of thecombustible gas by the combustion section 19 is disposed on the tip endof the combustion section 19, and is connected to one end of a heatexchanger 27. The main oxygen supply path 10 is disposed in the heatexchanger 27. When heat is exchanged between the waste gas and oxygenflowing through the main oxygen supply path 10, oxygen is heated.

The other end of the heat exchanger 27 is connected to a duct 26 b fordischarging the waste gas having exchanged heat with oxygen to theatmosphere via a blower fan 28 and funnel 29, and a cyclone 30, coolingtower 31, and bug filter 32 are disposed midway along the duct 26 b.

Furthermore, for the apparatus of the present embodiment, a dispenserguide pipe 33 for dispensing a part of the combustible gas introducedinto the combustion furnace 3 from the gasification furnace 1 isconnected midway to the gas passage 2 via a check valve 34, and thedispensed combustible gas is guided into an oil content collector 35.The oil content collector 35 is constituted of capacitors 36 a, 36 b forcondensing the dispensed combustible gas, and an oil separator 37 forfurther collecting a combustible component which is not condensed by thecapacitors 36 a, 36 b. The oil separator 37 is connected to thecombustion furnace 3 via a gas guide pipe 38, and the gas containing thecombustible component which cannot be separated even by the oilseparator 37 is introduced into the combustion section 19 of thecombustion furnace 3 via the gas guide pipe 38 and blower fan 39.

Storage tanks 40 a, 40 b for storing the condensed oil content aredisposed below the capacitors 36 a, 36 b. The oil content condensed bythe capacitors 36 a, 36 b is guided via a collected oil guide pipe 41from the storage tanks 40 a, 40 b, passed through an oil/water separator42 and filter 43, and fed to the fuel supply device 16 via a pump 44.

Additionally, in the apparatus of the present embodiment, a temperaturesensor 45 for detecting a temperature T₁ in the gasification furnace 1is attached to the upper part of the gasification furnace 1, and atemperature sensor 46 for detecting a temperature T₂ in the combustionfurnace 3 is attached to the combustion furnace 3 in a position oppositeto the tip end of the burner section 18. Detection signals of thetemperature sensors 45, 46 are inputted to the control device 14.

A waste incineration disposal method by the apparatus of the presentembodiment will next be described with reference to FIGS. 1 and 2.

In the apparatus shown in FIG. 1, when the waste A is incinerated anddisposed of, first the introduction door 4 of the gasification furnace 1is opened, and the waste A is introduced into the gasification furnace 1via the injection port 5. The waste A is a mixture of various wastesmainly of the waste tire, and regulated to have heat amount such thatcombustion temperature is 800° C. (first preset temperature) or moreduring continuation of combustion of the stable combustible gasgenerated by the dry distillation in the gasification furnace 1. In thepresent embodiment, the waste is further regulated to have the heatamount with the combustion temperature of 850° C. or more.

Subsequently, the introduction door 4 is closed to bring the interior ofthe gasification furnace 1 to a fully closed state, the combustiondevice 25 of the combustion furnace 3 is operated by the control device14 prior to ignition of the waste A, and thereby the combustion of thecombustion assistant oil is started. The temperature T₂ in thecombustion furnace 3 gradually rises by the combustion of the combustionassistant oil. When the temperature T₂ detected by the temperaturesensor 46 exceeds 800°C., the igniter 15 of the gasification furnace 1is operated by the control device 14, the waste A is ignited, andpartial combustion of the waste A starts. When the partial combustion ofthe waste A starts, the temperature T₁ in the gasification furnace 1gradually rises, the temperature T₁ detected by the temperature sensor45 reaches a preset temperature T_(1A), the control device then judgesthat the ignition is performed without any abnormality and the igniter15 is stopped.

During the ignition, the control valve 12 of the dry distillation oxygensupply path 9 is opened beforehand with a relatively small predeterminedopen degree via the valve drive unit 13 controlled by the control device14. As a result, the waste A is ignited by the igniter 15 using oxygenpresent in the gasification furnace 1, and a small amount of oxygensupplied to the gasification furnace 1 from the oxygen (air) supplysource 11 via the main oxygen supply path 10 and dry distillation oxygensupply path 9.

When the partial combustion of the waste A starts in the lower layerpart of the waste A in the gasification furnace 1 by the ignition, thedry distillation of the upper layer part of the waste A starts by thecombustion, and the combustible gas generated by the dry distillation isintroduced into the burner section 18 of the combustion furnace 3 viathe gas passage 2 connected to the gasification furnace 1. After theignition, according to a predetermined program, the control device 14gradually increases the open degree of the control valve 12 disposed inthe dry distillation oxygen supply path 9 in a stepwise manner. As aresult, a sufficient amount of oxygen necessary for the continuouscombustion is supplied to the lower layer part of the waste A, thecombustion of the lower layer part of the waste A is stabilized withoutbeing excessively enlarged, and the dry distillation of the upper layerpart of the waste A is stably be performed.

When the combustible gas is introduced into the burner section 18 of thecombustion furnace 3, the control valve 23 of the combustion oxygensupply path 22 is opened beforehand with the predetermined open degreeby the valve drive unit 24 controlled by the control device 14. Then,the combustible gas introduced into the burner section 18 is mixed withoxygen supplied via the combustion oxygen supply path 22 in the burnersection 18, is ignited by combustion flame supplied via the combustiondevice 25, and starts to be combusted with the combustion assistant oilin the combustion section 19.

At the start of the combustion of the combustible gas, the generation ofthe combustible gas by the dry distillation is unstable, and thecombustible gas is not stably supplied to the combustion furnace 3 insome cases. However, as the dry distillation in the gasification furnace1 becomes stable as described above, the combustible gas is continuouslygenerated, and generated amount also increases.

In this case, when the amount of generated combustible gas increases andthe temperature T₂ in the combustion furnace 3 rises, the combustiblegas can spontaneously and stably continue the combustion by its owncombustion heat. Therefore, when the temperature T₂ in the combustionfurnace 3 detected by the temperature sensor 46 reaches a second presettemperature above 800° C., for example, 830° C. or more, the controldevice 14 stops the combustion of the combustion assistant oil by thecombustion device 25. It is judged according to a change of thetemperature T₂ after the stop whether the combustible gas canspontaneously and stably continue the combustion.

That is to say, when the temperature T₂ in the combustion furnace 3falls below 830° C. after the stop of the combustion of the combustionassistant oil it is judged that the combustible gas is not ready to bespontaneously combusted, the combustion device 25 is re-ignited, and thecombustion of the combustion assistant oil is resumed. Moreover, whenthe temperature T₂ in the combustion furnace 3 reaches 830° C. or more,the combustion of the combustion assistant oil by the combustion device25 is stopped again, and an operation of judging whether the combustiblegas can spontaneously and stably continue the combustion is repeated.

As a result, the combustion of the combustion assistant oil by thecombustion device 25 is stopped when the temperature T₂ in thecombustion furnace 3 reaches 830° C. or more, and resumed when thetemperature falls below 830° C. The combustion is intermittentlyperformed in this manner, and the temperature T₂ in the combustionfurnace 3 changes in a zigzag manner as shown in FIG. 2. Moreover, evenafter stopping the combustion of the combustion assistant oil by thecombustion device 25, the temperature T₂ in the combustion furnace 3 ismaintained at 830° C. or more, the control device 14 then judges thatthe combustible gas is ready for spontaneous combustion by its owncombustion heat, and the combustion of the combustion assistant oil bythe combustion device 25 is finished. Thereafter, the spontaneouscombustion of only the combustible gas is performed, and the temperatureT₂ in the combustion furnace 3 detected by the temperature sensor 46substantially indicates the combustion temperature of the combustiblegas itself.

When the spontaneous combustion of only the combustible gas isperformed, the combustion temperature of the combustible gas itselfdetected as the temperature T₂ in the combustion furnace 3 is maintainedto be substantially constant at 830° C. or more, for example, at 850° C.In this case, the control device 14 automatically controls the opendegree of the control valve 23 of the combustion oxygen supply path 22so that the sufficient amount of oxygen necessary for the completecombustion of the combustible gas is supplied to the burner section 18.Concretely, the control is performed so as to reduce the open degree ofthe control valve 23 and decrease the oxygen supply amount to the burnersection 18, when the combustion temperature T₂ of the combustible gas inthe combustion furnace 3 falls below 850° C. Conversely, when thetemperature T₂ is higher than 850° C., the open degree of the controlvalve 23 is enlarged and the oxygen supply amount to the burner section18 is increased.

Moreover, the control device 14 automatically controls the open degreeof the control valve 12 in accordance with the combustion temperature T₂of the combustible gas in the combustion furnace 3, detected by thetemperature sensor 46, and thereby adjusts the amount of the generatedcombustible gas in the gasification furnace 1, so that the combustiontemperature T₂ of the combustible gas in the combustion furnace 3 ismaintained to be substantially constant at 850° C. Concretely, thecontrol is performed so as to increase the open degree of the controlvalve 12, increase the oxygen supply amount to the gasification furnace1, and promote the generation of the combustible gas by the drydistillation, when the combustion temperature T₂ of the combustible gasin the combustion furnace 3 is lower than 850° C. Conversely, thecontrol is performed so as to reduce the open degree of the controlvalve 12, decrease the oxygen supply amount to the gasification furnace1, and inhibit the generation of the combustible gas by the drydistillation, when the combustion temperature T₂ of the combustible gasin the combustion furnace 3 is higher than 850° C. Thereby, in thegasification furnace 1 the combustion of the lower layer part and thedry distillation of the upper layer part of the waste A stably progress,and the temperature T₂ in the combustion furnace 3 is maintained to besubstantially constant at 850° C. as shown in FIG. 2.

Furthermore, the temperature T₁ in the gasification furnace 1 detectedby the temperature sensor 45 rises with the combustion of the lowerlayer part of the waste A immediately after the waste A is ignitedduring operation of the combustion device 25, and thereafter drops oncebecause the combustion heat of the lower layer part of the waste A isconsumed by the dry distillation of the upper layer part. Subsequently,the combustion device 25 is stopped, and the spontaneous combustion ofonly the combustible gas is performed. Then, in a stage in which the drydistillation stably progresses in a stationary manner (the temperatureT₂ in the combustion furnace 3 is maintained to be substantiallyconstant at 850° C.), the temperature T₁ in the gasification furnace 1gradually rises with the progress of the dry distillation.

In the stage in which only the combustible gas is spontaneouslycombusted, the generation of the combustible gas progresses. Even when apart of the combustible gas is dispensed, a sufficient amount ofcombustible gas can be obtained to maintain the temperature T₂ in thecombustion furnace 3 to be substantially constant at 850° C. Therefore,in this stage, as described above, a part of the combustible gas isdispensed by the dispenser guide pipe 33, and the combustible componentcontained in the combustible gas is collected as an oil content by theoil content collector 35.

Subsequently, the dry distillation progresses, and the portion of thewaste A able to be dry-distilled becomes short. In this case, even whenthe open degree of the control valve 12 of the dry distillation oxygensupply path 9 is adjusted to increase the oxygen supply amount to thegasification furnace 1, a sufficient amount of combustible gas formaintaining the temperature T₂ in the combustion furnace 3 to besubstantially constant at 850° C. cannot be generated. In this state,the temperature T₂ in the combustion furnace 3 tends to drop from 850°C.

Then, the control device 14 resumes the combustion of the combustionassistant oil by the combustion device 25, when the temperature T₂ inthe combustion furnace 3 reaches a third preset temperature in a rangeof 800° C. to 850° C., for example, 830° C. In this stage, when thetemperature T₂ in the combustion furnace 3 reaches 830° C. or more, thecontrol device 14 stops the combustion of the combustion assistant oilby the combustion device 25, and judges, according to the change of thetemperature T₂ in the combustion furnace 3 after the stop, whether thecombustible gas can spontaneously and stably continue the combustion.

That is to say, when the temperature T₂ in the combustion furnace 3falls below 830° C. after the stop of the combustion of the combustionassistant oil, the control device 14 Judges that the combustible gascannot spontaneously be combusted by the own combustion heat, actuatesthe combustion device 25 again, and resumes the combustion of thecombustion assistant oil. Moreover, when the temperature T₂ in thecombustion furnace 3 reaches 830° C. or more, the control device repeatsthe operation of stopping again the combustion of the combustionassistant oil by the combustion device 25 and judging whether thecombustible gas can spontaneously and stably continue the combustion.

As a result, the combustion of the combustion assistant oil by thecombustion device 25 is stopped when the temperature T₂ in thecombustion furnace 3 is 830° C. or more, resumed when the temperaturefalls below 830° C., and intermittently performed in this manner. Inthis case, the temperature T₂ in the combustion furnace 3 changes in azigzag manner as shown in FIG. 2. Subsequently, when the temperature T₂in the combustion furnace 3 cannot be raised to 830° C. or more even bythe combustion of the combustion assistant oil by the combustion device25, the control device 14 judges that the combustible gas cannotspontaneously be combusted, continuously combusts the combustionassistant oil by the combustion device 25 and maintains the temperatureT₂ in the combustion furnace 3 at 800° C. or more.

On the other hand, when the portion of the waste A able to bedry-distilled becomes poor, the waste A is brought to an entirecombustion state, and the temperature T₁ in the gasification furnace 1rapidly rises. Subsequently, the temperature in turn decreases from amaximum temperature T_(MAX) at which the portion of the waste A able tobe dry-distilled is eliminated and the red heated waste A starts to beashed. However, since the capacity, material, and the like of the wasteA are various, a part of the waste is red-heated or not red-heated underthe ashed surface layer, and the temperature T₁ in the gasificationfurnace 1 sometimes rises again because of the heat of this part.

Therefore, when the temperature T₂ in the combustion furnace 3 fallsbelow 830° C., the control device 14 compares the temperature T₁ in thegasification furnace 1 detected by the temperature sensor 45 with themaximum temperature T_(MAX) in the gasification furnace 1 everypredetermined time, for example, every ten minutes. Subsequently, whenthe temperature T₁ in the gasification furnace 1 consecutively indicatesthe temperature being less than the maximum temperature T_(MAX)predetermined times, for example, three times, it is judged that thewaste A in the gasification furnace 1 securely and entirely shifts tothe ashing stage.

Thereafter, the temperature T₁ in the gasification furnace 1 indicates afourth preset temperature, for example, falls below 200° C. which isless than a dioxins generation temperature. Then, it is judged that thecombustible gas does not contain dioxins and that it is unnecessary tomaintain the temperature T₂ in the combustion furnace 3 at 800° C. ormore, and the combustion of the combustion assistant oil by thecombustion device 25 is finished.

Subsequently, the ashing of the waste A progresses In the gasificationfurnace 1. Moreover, with the degrease of the portion of the waste Aable to be dry-distilled, the amount of the combustible gas decreases inthe combustion furnace 3, and the spontaneous combustion cannot bemaintained. As a result, the temperature Tin then gasification furnace 1and the temperature T₂ in the combustion furnace 3 gradually drop,thereby resulting in natural extinction.

A method of collecting the oil content from a part of the combustiblegas by the oil content collector 35 will next be described.

In the present embodiment, in the stage of the stable combustion of thecombustible gas in the combustion furnace 3 (in the stage in which thetemperature T₂ in the combustion furnace 3 is maintained to besubstantially constant at 850° C.), much combustible gas is generated inthe gasification furnace 1. Therefore, when a pressure of thecombustible gas in the gas passage 2 exceeds a predetermined magnitudein the stage of stable dry distillation, a part of the combustible gaspasses the check valve 34 of the dispenser guide pipe 33 and isintroduced into the oil content collector 35. For the combustible gasintroduced into the oil content collector 35, the combustible componentwhich is easily liquefied is first condensed in the capacitors 36 a, 36b arranged in series, and the liquefied oil content is contained in thestorage tanks 40 a, 40 b. The oil content is extracted by the pump 44,refined by the oil/water separator 42 and filter 43, subsequently fed tothe fuel supply device 16, and used as a part of the combustionassistant oil in the next operation of the combustion device 25.

Subsequently, the combustible gas is fed to the oil separator 37, andthe combustible component which as not been condensed in the capacitors36 a, 36 b is collected as the oil content. Moreover, the remainingcombustible gas containing the combustible component which has not beencollected even by the oil separator 37 is introduced into the combustionsection 19 of the combustion furnace 3 from the gas guide pipe 38 viathe blower fan 39 and combusted.

Discharge of waste gas of the combustion furnace 3 will next bedescribed.

In the present embodiment, waste gas of the combustion furnace 3 isfirst fed to the heat exchanger via the duct 26 a, and used in heatingoxygen flowing through the main oxygen supply path 10 disposed in theheat exchanger 27. Since the heated oxygen is introduced into thecombustion furnace 3 via the combustion oxygen supply path 22 to raisethe temperature T₂ in the combustion furnace 3, the fuel supplied fromthe fuel supply device 16 can be saved during the operation of thecombustion device 25. Moreover, in the stage of the stable drydistillation, the amount of the combustible gas necessary formaintaining the temperature T₂ in the combustion furnace 3 to besubstantially constant at a preset temperature T_(2A) is reduced, andthe amount of the combustible gas able to be dispensed via the dispenserguide pipe 33 can be increased.

Furthermore, when heated oxygen is introduced into the gasificationfurnace 1 via the dry distillation oxygen supply path 9, an effect thatthe combustion of the waste A is further stabilized can also beobtained.

The waste gas used in heating oxygen in the heat exchanger 27 isintroduced into the cyclone 30 via the duct 26 b, and dust contained inthe waste gas is removed. Subsequently, the waste gas is introduced intothe cooling tower 31 and sufficiently cooled, and is then introducedinto the bug filter 32. Subsequently, after fine flied ash is removedfrom the waste gas by the bug filter 32, the waste gas is finallydischarged to the atmosphere via the blower fan 28 and funnel 29.

What is claimed is:
 1. A waste incineration disposal method comprisingsteps of: combusting a part of a waste contained in a gasificationfurnace, and dry-distilling the other part of the waste by a combustionheat; and introducing a combustible gas generated by the drydistillation into a combustion furnace to combusted the combustible gas,wherein when the combustible gas is combusted in the combustion furnace,oxygen required for the combustion is supplied to the combustion furnacein accordance with an amount of the combustible gas introduced into thecombustion furnace to combusted the combustible gas, an amount of oxygensupplied to the gasification furnace is controlled in accordance with atemperature change in the combustion furnace caused by the combustion ofthe combustible gas in the combustion furnace, the amount of thecombustible gas generated by the dry distillation is adjusted, and thetemperature in the combustion furnace is maintained at a first presettemperature or more, said waste incineration disposal method furthercomprising steps of: containing in the gasification furnace the wasteregulated to generate the combustible gas having a heat amount forsetting the temperature in the combustion furnace at the first presettemperature or more, combusting fuels other than the combustible gas inthe combustion furnace prior to ignition of the waste, igniting thewaste to start dry distillation and combusting the generated combustiblegas with the other fuels when the temperature in the combustion furnacereaches the first preset temperature or more, and finishing thecombustion of the other fuels when the temperature in the combustionfurnace reaches a second preset temperature higher than the first presettemperature or more by the combustion of only the combustible gas;maintaining the temperature in the combustion furnace to besubstantially constant at the second preset temperature or more bycombusting only the combustible gas; resuming the combustion of theother fuels and combusting the combustible gas with the other fuels whenthe temperature in said combustion furnace falls below a third presettemperature lower than the substantially constant temperature and higherthan the first preset temperature, maintaining the temperature in thecombustion furnace at the first preset temperature or more, andfinishing the combustion of the other fuels when the temperature in thegasification furnace falls below a fourth preset temperature, whereinsaid fourth preset temperature is lower than a maximum temperature inthe gasification furnace.
 2. The waste incineration disposal methodaccording to claim 1 wherein the first preset temperature is atemperature at which dioxins can thermally be decomposed.
 3. The wasteincineration disposal method according to claim 1 or 2 wherein the firstpreset temperature is 800° C. or more.
 4. The waste incinerationdisposal method according to any one of claims 1 or 2 wherein the fourthpreset temperature is less than a dioxins generation temperature.
 5. Thewaste incineration disposal method according to any one of claims 1 or 2wherein in a period from the ignition of said waste until thetemperature in said combustion furnace reaches the second presettemperature or more by the combustion of only said combustible gash saidcombustion of the other fuels is intermittently performed by stoppingthe combustion of the other fuels when the temperature in the combustionfurnace reaches the second preset temperature or more, and re-ignitingthe waste when the temperature in the combustion furnace falls below thesecond preset temperature after the stop, and the intermittentcombustion of the other fuels is finished when the temperature in thecombustion furnace is not less than the second preset temperature evenafter the stop of the combustion of the other fuels.
 6. The wasteincineration disposal method according to any one of claims 1 or 2wherein in a period from when the temperature in said combustion furnacefalls below the third preset temperature until the temperature in saidgasification furnace falls below the fourth preset temperature, saidcombustion of the other fuels is intermittently performed by stoppingthe combustion of the other fuels when the temperature in the combustionfurnace reaches the third preset temperature or more, and re-ignitingthe waste when the temperature in the combustion furnace falls below thethird preset temperature after the stop, the combustion of the otherfuels is continuously performed to maintain the temperature in thecombustion furnace at the first preset temperature or more when thetemperature in the combustion furnace falls below the third presettemperature even after the re-ignition, and the combustion of the otherfuels is finished when the temperature in said gasification furnacefalls below the fourth preset temperature.
 7. The waste incinerationdisposal method according to claim 6 wherein when the temperature insaid gasification furnace is detected every predetermined time, it isconsecutively detected predetermined times that the temperature in thegasification furnace is less than the maximum temperature in thegasification furnace, and the temperature in the gasification furnacefalls below the fourth preset temperature, said combustion of the otherfuels is finished.
 8. The waste incineration disposal method accordingto claim 1 wherein when said combustible gas generated by the drydistillation of the waste in said gasification furnace is introducedinto said combustion furnace and combusted, a part of the combustiblegas is dispensed and condensed, and an oil content is collected from thepart of the combustible gas and used as said other fuels.
 9. The wasteincineration disposal method according to claim 1 wherein when saidother fuels are combusted, oxygen heated by the heat of said combustionfurnace is supplied to said combustion furnace.